The compound 1,1,1,3,3-pentachloropropane (HCC-240fa) is a raw material for producing 1,1,1,3,3-pentafluoropropane (HFC-245fa), which is a non-ozone depleting chemical and can be used as blowing agent, energy transfer medium, and so on. Addition reactions for preparing useful haloalkanes, such as HCC-240fa, are known in the art. For example, U.S. Pat. No. 6,313,360 teaches a process for producing HCC-240fa by reacting carbon tetrachloride (CCl4) and vinyl chloride (VCM) in the presence of a catalyst mixture comprising organophosphate, e.g., tributylphosphate (TBP), metallic iron and ferric chloride under conditions sufficient to produce a product mixture containing HCC-240fa. The 240fa product is then recovered by separating it from reactants, catalyst and by-products. See also, U.S. Pat. Nos. 5,902,914, 6,187,978, 6,500,995, 6,552,238, 6,720,466, 7,112,709, and U.S. Patent Publication No. 2008/0091053. The disclosures of all of these references are hereby incorporated herein by reference.
Applicants have unexpectedly discovered that when using the catalyst mixture disclosed in U.S. Pat. No. 6,313,360, namely, TBP, metallic iron, and ferric chloride, substantial amounts of CCl4 originating by-products such as hexachloroethane, tetrachloroethene, chloroform, and hexachlorobutadiene are generated during the reaction of CCl4 and VCM, especially during the start-up of the reaction. The formation of these by-products causes a significant decrease in the HCC-240fa selectivity.
Therefore, the present inventors have come to appreciate the need for an improved start-up process for the manufacture of HCC-240fa. Embodiments of the present invention solve this problem.
Applicants have also discovered that after the initial start-up described above, e.g., when this reaction is conducted as a batch or preferably, as a continuous operation, the reactor eventually contains a concentrated amount of HCC-240fa, e.g., having a composition of potentially greater than 60 wt % of the reactor organic content. Under these circumstances, when fresh catalyst consisting of iron powder (Fe0) and tributylphosphate (TBP), is introduced into the reactor, the VCM preferentially reacts with the HCC-240fa, instead of the CCl4 to form undesirable by-products such as 1,1,3,3,5,5-hexachloro-pentane (major) and 1,1,1,3,5,5-hexachloropentane (minor). For convenience purpose, these hexachloropentanes are called vinyl chloride originating by-products. Depending on the TBP concentration, the selectivity to 1,1,3,3,5,5-hexachloropentane can reach 65%, which causes a substantial yield loss of the desired HCC-240fa product.
Therefore, the present inventors have come to appreciate a need for means by which the formation of these vinyl chloride originating by-products can be avoided during this process. Embodiments of this invention also provide a solution to this problem.